Metal seal rings are currently used on some electronic device packages which utilize brazing as the method of attaching the seal ring to the ceramic base. Since the brazing is done at temperatures in excess of the melting point of aluminum, any coating of the bonding pads with aluminum must be done after the package is assembled. The metal sealing ring must also be plated after assembly which can result in plating salt residue being left on the package surfaces or crevices.
According to this invention, electronic device packages can be constructed from alumina ceramics and metal leadframes which are sealed together with a low temperature solder glass to form a hermetic seal. This low temperature processing allows the use of aluminum bonding fingers which cannot be done with packages processed at temperatures above the melting point of aluminum. Final sealing is normally accomplished according to the invention by sealing a ceramic lid onto the subassembly using the same solder glass at temperatures which are not detrimental to the electronic device.